A variety of visual and visual-motor functions are poorly sustained by isoluminant chromatic stimuli. For example, stereograms made up of black and white bars are readily seen in depth, but under the right conditions stereograms made up of two different colors (such as red and green) matched in luminance do not yield a sensation of depth. For each color pair, a pair of relative luminances can be found that will make stereopsis disappear. In other cases, some color pairs do worse than others in sustaining visual function; for example, borders made up from color combinations known as tritan pairs virtually disappear. Such phenomena are of great theoretical interest, because they suggest that certain of the postreceptoral channels of color vision may not have access to the neural processing mechanisms that carry out these visual functions. The goals of this research are: 1. To replicate and systematize observations of these losses of chromatic information for a series of visual functions: the pupillary responses, the perception of borders, binocular rivalry, stereopsis, vernier acuity, and motion. 2. To study the spatial and temporal processing abilities (contrast sensitivity functions) of the postreceptoral channels of human color vision. 3. To analyze theoretically whether the (presumably limited) spatial and temporal processing abilities of the color channels can account for these losses of chromatic information, or whether these chromatic losses constitute de novo losses of information in human visual processing.